1. Field of the Invention
The present invention relates to an apparatus and method for fixation of soft tissue to bone. More specifically, the present invention relates to sutureless arthroscopic apparatus and methods for anchoring soft tissue to bone using a headed bio-absorbable tissue anchor.
2. Description of the Related Art
When soft tissue tears away from bone, reattachment becomes necessary. Various fixation devices, including sutures, screws, staples, wedges, and plugs have been used in the past to secure soft tissue to bone. More recently, various types of threaded suture anchors have been developed.
The known suture anchors generally require that the surgeon tie knots in the suture to secure tissue to the bone. Tying surgical knots is tedious and time-consuming. It would be preferable to be able to secure the soft tissue to the bone in one step without having to tie knots.
Accordingly, a need exists for a bioabsorbable anchor for soft tissue fixation that can be installed to secure tissue easily and effectively without sutures. A need also exists for a soft tissue fixation device that displaces a minimum amount of bone upon insertion. In addition, a need exists for a tissue fixation device having exceptional pull-out strength, especially in soft bone.
The present invention overcomes disadvantages of the prior art, such as those noted above, by providing a headed bioabsorbable tissue anchor having a thread spiraling helically around a central body, in which the head of the anchor engages the soft tissue for fixation to bone.
The headed bioabsorbable tissue anchor of the present invention has a cannulated, threaded central body. A flat, disk-shaped head is provided on the proximal end of the anchor. The disk-shaped head engages soft tissue for fixation as the anchor is installed through soft tissue and into bone.
The central body of the anchor tapers toward the distal end. The distal tip preferably is flat to avoid tip breakage, as could occur with a pointed tip.
The anchor is formed of a bioabsorbable PLA copolymer, preferably poly (L/D-lactide) acid.
Surgical installation is achieved using a driver that engages the disk-shaped head for installing the threaded anchor by turning into the bone. The anchor has at least one opening for engagement with the end of a driver.
The outer circumferential dimension of the disk-shaped head advantageously is substantially larger than the circumference of the central body. Accordingly, the enlarged head engages tissue and holds it in place against the bone into which the tissue anchor has been installed.
Advantageously, the threads of the headed bioabsorbable tissue anchor of the present invention have a cancellous thread design that provides an increased percentage of thread surface area for each turn of the anchor, as compared with known anchors, thus providing increased pull-out strength, and a decreased tendency for back-out. The cancellous thread design is similar to the metal suture anchor described in U.S. Pat. No. 6,214,031, issued Apr. 10, 2001, the entire disclosure of which is incorporated herein by reference.
In addition to increased pull-out strength, the one piece sutureless design of the implant advantageously eliminates suture management issues, and simplifies the arthroscopic surgical technique. Further, revisions are simplified, and the biocompatible PLA copolymer material will not interfere with MRI or CT scans. The wide, low profile head provides a broad area of tissue to bone contact without impingement on other tissues. Also, the cannulated design allows the use of a guide wire to ensure accurate implant placement. The implant also can be used in open procedures.
Other features and advantages of the present invention will become apparent from the following description of the invention, which refers to the accompanying drawings.